Ah, so you're saying (if I'm reading this correctly) that the plane only carries the carbon portion of the CO2, and the oxygen comes from the air itself. That's how it's emitting more CO2 then it's fuel mass.
Correct. Fuel is around 16/36th of the CO2 mass it emit when being burnt. A 777 carries around 120 tons of fuel for a SF/LON flight, so that's around 300 tons of emissions per flight.